Process of drawing steel



Patented Dec. 30, 11941 UNlTED STATES PATENT OFFICE azsaszs raocnss or nnawme s'mnn GerhardRoosner, Ludwig Schuster, and Helmuth Ley, Frankfort-on-the-Main, Germany, assignors to American Lnrgl Corporation, New York, N. Y., a corporation of New York No Drawing. Application September 18, 1939.

$331 No. 295,540. In Germany September 20,

6 Claims.

The invention relates to a process of drawing steel, and particularly to the drawing of so-called stainless steel.

The invention involves a novel treating step which precedes the drawing, this step making possible the cold working or cold drawing of high grade steels of austenitic structure, particularly stainless steels containing chromium 'and/or nickel. r

In the past it has been impossible or diflicult to subject such steels to cold working and particularly to cold drawing. Such working has therefore required aheating of the steel with an increase in expense and possible injury to the steel itself.

. The primary object of the present invention is to provide a treatment which will render the steel capable of being easily cold-worked, and particularly cold-drawn.

In general, the invention includes as its essential step the treatment of the steel with an acid solution containing an easily hydrolyzable ferric salt. While other acids and particularly the known pickling acids may be useful, the halogen acids, and particularly hydrochloric acid, are most. satisfactory.

In the preferred form of the invention, use of oxidizing agents in the treating bath is avoided, and preferably a pure hydrochloric acid is'used as the acid treating agent.

The following example will demonstrate one method of carrying out the invention:

An austenitic steel of the stainless type con- I taining 18% chromium and 8% nickel was treated for five minutes at a temperature of 98 C. with a pickling bath of the following composition:

Parts byvolume Water 300 H2804 (specific gravity 1.84); 140 HCi (specific gravity 1.19) 160 --10% aqueous solution of potassium persul- As addition agents, any easily hydrolizable ferric salt may be useful. The preferred salt, however, to be used according to the invention is ferric acetate. The .proportion of ferric salt should preferably be such that hydrolysis of the ferric salt takes place on the surface of the metal through-the consumption of the acid.

The treating step is carried out in the conven-- tional manner usual in pickling, and the material is than capable of being cold-drawn.

phate 600 The pickled steel was then removed from this bath and treated at a temperature of from 90 C. to 95 C. for 20 minutes in an equeous solution containing the following amounts of active materials per liter:

19 gr. hydrochloric acid I 10 gr. anhydrous ferric acetate After this treatment the steel was provided with a usual drawing lubricant such as wool fat and then cold-drawn. It was found that cold drawing was possible and was quite simple.

While we have described herein some embodiments of our invention we wish it to be understood that we do not intend to limit ourselves thereby except within the scope of the appended claims.

We claim:

'1. A process of cold drawing stainless steel which comprises treating the steel with a solution of hydrochloric acid which contains easily hydrolizable. ferric salts, and then drawing the steel so treated. a H

Further improvement in ductility can be ob- 'tained if the steel is treated with conventional pickling agents normally used with high grade or stainless steels before it is subjected to the pro-- oedure described above. Use may be made for thisstep of mixtures of hydrochloric acid and nitric acid; of sulphuric acid and hydrochloric acid; of

I nitric and hydrofluoric acids; or of nitricfhydrochloric and hydrofluoric acids. It is particularly desirable to utilize in additoi'n to hydrochloric acid and sulphuric acids a substance capable of yieldihg active oxygen'whioh may thus oxidize the hydrochloric acid. Potassium persu'lphate is an example of such a substance.

2. A process of cold drawing stainless steel which comprises treating the steel with a solution of hydrochloric acid which contains easily hydrolizable ferric salts, in such concentration that hydrolysis of such salts takes" place on the .Iects which comprises first pickling the steel,

2 2,268,525 then treating the steel in a solution of hydrothe steel in a solution of hydrochloric acid which chloric acid which contains an easily hydrolyzacontains an easily hydrolyzalile ferric salt, and ble ferric salt, and then drawing the steel. then drawing the steel.

6. A process of cold working stainless steel objects which comprises first pickling the steel in a 5 GERHARD ROESNER. pickling mixture containing an oxidizing agent LUDWIG SCI-IUSTER.

capable of releasing free oxygen, then treating HELMUTH LEY. 

